1. Field of the Invention
The present invention relates to a technique of creating a computer-vision-enabled ophthalmic augmented reality environment for the diagnosis and treatment of eye diseases, and more particularly, to a technique for superimposing present and previous images to aid in the recognition and treatment of diseased tissue in the eye. The ophthalmic augmented reality platform also serves as a paradigm for telecollaboration, telemedicine, and teaching.
2. Description of the Prior Art
Diabetic macular edema and age-related macular degeneration (AMD) are the two major causes of visual loss in developed countries. While laser therapy for these and other diseases has prevented loss of visual function in many individuals, disease progression and visual loss following suboptimal treatment is common. For AMD, there is unambiguous evidence that incomplete laser photocoagulation of the border of a choroidal neovascular lesion is associated with an increased risk for further visual loss, while treatment beyond the borders unnecessarily destroys viable, central photoreceptors, further degrading visual function.
As a concrete example, in eyes with juxtafoveal choroidal neovascularization (CNV) secondary to ocular histoplasmosis, only 5% of eyes with laser treatment that covered the foveal side of the lesion with a narrow (&lt;100.mu.) treatment border suffered severe visual acuity loss, while approximately 25% of eyes with either some of the foveal side untreated, or a wide border of treatment on the foveal side suffered severe visual loss. Macular Photocoagulation Study Group, "The Influence of Treatment Extent on the Visual Acuity of Eyes Treated With Krypton Laser For Juxtafoveal Choroidal Neovascularization," Arch. Ophthalmol., Vol. 113, pp. 190-194, 1995. Similar results have been reported for AMD.
Building on the recommendations proposed in Macular Photocoagulation Studies, clinicians generally attempt to correlate angiographic data with biomicroscopic images using crude manual, time-consuming, potentially error-prone methods. In a recent practical review in an article entitled "How to Be More Successful in Laser Photocoagulation," Ophthal. Times, pp. 103-108, 1996, Neely suggests that " . . . to assist you in treatment (of neovascular AMD), project an early frame of the fluorescein angiogram onto a viewing screen. Use the retinal vessels overlying the CNV lesion as landmarks. I suggest tracing an image of the CNV lesion and overlying vessels onto a sheet of onion skin paper. It takes a little extra time, but I find it helps to clarify the treatment area." Accordingly, precise identification of the treatment border during laser therapy by correlating the biomicroscopic image with fluorescein angiographic data should be beneficial for maximizing post-treatment visual function. Diagnosis and treatment relies on synthesizing clinical data derived from fundus biomicroscopy with angiographic data, but, at present, methods for correlating these data, and for direct guidance of laser therapy, do not exist.
As noted by O'Toole et al. in an article entitled "Image Overlay for Surgical Enhancement and Telemedicine," Interactive Technology and the New Paradigm for Healthcare, K. Morgan et al., editors, IOS Press, 1995, although there has been an explosive development of investigation into virtual reality applications in medicine, augmented reality applications might have a far greater utility, but have received much less attention. An early study by Bajura et al. reported in an article entitled "Merging Virtual Objects With the Real World: Seeing Ultrasound Imagery Within the Patient," Computer Graphics, Vol. 26, pp. 203-210, 1992, described the superposition of ultrasound images on the abdomen, using a position-tracked, see-through head mounted display. Recently, there has been great interest in neurosurgical applications of augmented reality. Specifically, it has been noted by Gleason et al. in an article entitled "Video Registration Virtual Reality for Nonlinkage Stereotactic Surgery," Stereotactic Funct. Neurosurgery, Vol. 63, pp. 139-143, 194, by Edwards et al. in an article entitled "Neurosurgical Guidance Using the Stereo Microscope," Proc. First Int. Conf. Computer Vision, Virtual Reality and Robotics in Medicine, Nice, France, pp. 555-564, and by Grimson et al. in an article entitled "An Automatic Registration Method for Frameless Stereotaxy, Image Guided Surgery, and Enhanced Reality Visualization," IEEE Trans. Medical Imaging, Vol. 15, p. 129, 1996, that the intraoperative registration of CT, MR, and PET images on a living patient in the operating room may greatly facilitate surgical planning and execution. Typically, registration of the patient with the radiographic data is accomplished by tracking fiducial markers placed on the skin surface and tracking the position of the operating microscope. However, for ophthalmic applications, a technique is required that does not require fiducial markers or image tracking whereby a real-time image can be registered with a previously stored, montaged data set.
Moreover, methods for highly accurate real-time image comparison in AMD, cytomegalic virus retinitis, and diabetic retinopathy, for example, do not exist, and an appropriate platform for telecollaboration, telemedicine, and teaching has not heretofore been described. An ophthalmic augmented reality platform for this purpose is desired.
The present invention is directed to these needs in the art.